In the 3rd Generation (3G) and the Beyond 3rd Generation (B3G) communication systems, the coverage area is an important aspect for a wireless access system, and the wireless access system performs coverage of its service area generally through base stations or access points. However, a mobile station may quite possibly locate outside the service area and can not therefore share the wireless access service due to its mobility. Even if the UE locates in the service area, the signal transmission may be possibly obstructed by obstacles on transmission paths, which reduces the Quality of Service. In addition, very high speed data (e.g., 1 Gbps) shall be transmitted in future mobile communication systems, and it is extremely possible that a high communication frequency (e.g., 5 GHz) is utilized in the future mobile communication systems due to the limitation of frequency band allocation. These two factors may cause a sharp reduction of the coverage area, and the number of base stations/access points may influence construction and operating cost of the network to a large extent.
In consideration of the above, the Relay or Relay Station (RS) technology is generally proposed in the future mobile communication technical solution in order to address the seamless coverage of service area and the increasing of system capacity and to save the cost as soon as possible. If a UE locates outside the service area or the quality of signal can not meet the requirements, the signal may be relayed by a RS to implement extension of the service area or improve transmission reliability, i.e., the main function of the Relay is to extend the coverage area and the cell capacity. A basic structure of the Relay may be depicted in FIG. 1. In FIG. 1, if the RS transmits independent synchronization and control information, the RS is called a non-transparent relay, otherwise the RS is called a transparent relay.
In the conventional art, in order to keep a strong compatibility with the conventional 3G (mainly the TD-SCDMA), a frame structure of B3G is illustrated in FIG. 2. In addition, in order to keep a strong compatibility with the conventional 3G (mainly the TD-SCDMA), a frame structure of the Long term evolution time division duplex (LTE TDD) is illustrated in FIG. 3. In order to support the relay, a downlink subframe and an uplink subframe are generally divided into Access Zones and Relay Zones respectively in the TDD system, as particularly illustrated in FIG. 4.
However, the above TDD system supporting the Relay frame structure has the following apparent disadvantages if it is applied to the B3G technology:
(1) Increasing the delay. Taking a BS transmitting downlink traffic as an example: when the downlink traffic arrives at the BS, the BS may transmit the downlink traffic at the beginning time of a downlink subframe in the original system frame structure. However, the BS may transmit the downlink traffic only in the DownLink (DL) Access Zone of the B3G frame structure supporting Relay, which increases the delay virtually and makes it difficult to meet the rigorous requirements for delay in B3G, as particularly illustrated in FIG. 5.
(2) Wasting resource. In the case that traffic is little and little bandwidth is required in a relay link, bandwidth in the whole Relay zone shall be allocated to the relay link if the original frame structure supporting Relay is utilized for data transmission, which may cause a severe resource wasting, as particularly illustrated in FIG. 6.